实在是写不出来。
<!DOCTYPE HTML>
<html >
<head>
<meta http-equiv="Content-Type" content="text/html; charset="utf-8" />
<title>流程控制语句</title>
<script type="text/javascript">
var infos=[["小A","女","21","大一"],["小B","男","23","大三"],["小C","男","24","大四"],["小D","女","21","大一"],["小E","女","22","大四"],["小F","男","21","大一"],["小G","女","22","大二"],["小H","女","20","大三"],["小I","女","20","大一"],["小J","男","20","大三"],];
//第一次筛选，找出都是大一的信息
var n=0;
var myarr=[];
for(var i=0;i<infos.length;i++)
{
if(infos[i][3]=="大一"){
myarr[n]=infos[i];
document.write(myarr[n]+"<br>");
n=n+1;
}
}
document.write(myarr.length+"<br>");
//第二次筛选，找出都是女生的信息
for(var a=0;a<myarr.length;a++){
switch(myarr[a][1]){
case "女":
document.write(myarr[a][0]+"<br>");
break;
default:
break;
}
}
</script>
</head>
<body>
</body>
</html>